Linkage Isomerism in Coordination Polymers

The use of the recently prepared polynitrile ligand tcnopr3OH(-) ([(NC)(2)CC(OCH2CH2CH2OH)C(CN)(2)](-)) with different salts of Fe(II), Co(II), and Ni(II) has led to a very rare example of linkage isomerism in a coordination chain. These pairs of linkage isomers can be formulated as [M(tcnopr3OH-kappa N,kappa O)(2)(H2O)(2)]; M = Fe (1), Co (3), and Ni(5) and [M(tcnopr3OH-kappa N,kappa N')(2)(H2O)(2)]; M = Fe (2), Co (4), and Ni (6). Compounds 1-2, 3-4, and 5-6 are three pairs of linkage isomers since they present the same formula and chain structure and they only differ in the connectivity of the polynitrile ligand bridging the metal ions in the chain: through a N and an O atom (1KN:2 kappa O-isomer) or through two N atoms (1 kappa N:2 kappa N'-isomer). The magnetic properties show, as expected, very similar behaviors for both isomers.